This invention relates to polymerizable compounds, some of which are surfactants, and to uses thereof, e.g. as an emulsifier in emulsion polymerization, and to latices produced by emulsion polymerization utilizing the polymerizable compounds.
The use of latices, produced by emulsion polymerization, in the production of paints or coatings for substrates is well know in the art. However, adhesion of such paints or coatings to the substrates is generally adversely affected by the presence of emulsifiers required in the emulsion polymerization process. For example, such emulsifiers affect adhesion and particularly wet adhesion in numerous ways. The emulsifiers tend to migrate to the surface during the drying process and collect at the interface of the paint or coating and the substrate forming a layer that is of greater sensitivity to moisture and reduces adhesion. Additionally, many such emulsifiers are generally incompatible with the other coating or paint components and tend to segregate, carry water and cause haze formation. It is therefore desirable that there be available polymerizable monomers that enable one to eliminate or decrease the amount of such emulsifiers required in the emulsion polymerization process.
This invention provides a process for the production of high monoester content polyalkylene oxide (meth)acrylate polymerizable phosphate esters, and processes to produce emulsion polymers of such polymerizable monomers and the resulting emulsion polymer products. The polymerizable polyalkylene oxide (meth)acrylate polymerizable phosphate esters produced by the process of this invention have a high mono/di-ester content, i.e., 80/20 or greater, and produce emulsion polymers of greatly improved properties compared to emulsion polymers produced from phosphate esters of lower mono/di-ester content.
The method comprises reacting exclusively a stoichiometrically effective amount of phosphoric anhydride with phosphoric acid to produce a phosphation reagent having an effective equivalent polyphosphoric acid weight percent of from about 118 to 125, and reacting the phosphonation reagent with an alcohol medium of the formula R1xe2x80x94C(O)xe2x80x94R2xe2x80x94Oxe2x80x94H, wherein R1 and R2 are as defined herein after, to produce a resulting ester composition wherein in the resulting ester compositions, the mono-ester to di-ester weight ratio is greater than 80:20 and the weight percent of the residual of said alcohol and phosphoric acid are individually each less than 6%, and the polymerizable compounds in the ester composition have the formula
R1xe2x80x94C(O)xe2x80x94R2xe2x80x94OPO3H2 
wherein:
R1 is an optionally substituted vinyl radical, preferably CH2xe2x95x90CHxe2x80x94, CH2xe2x95x90C(CH3)xe2x80x94, or cis-CH(COOH)xe2x95x90CHxe2x80x94, and
R2 is a divalent polyoxyalkylene radical having at least two oxyalkylene units, preferably about 2 to about 50 oxyalkylene units, more typically about 2 to about 20 oxyalkylene units, e.g. (Oxe2x80x94CH2CH2)n or (Oxe2x80x94CH2CH(CH3))n wherein n is from about 2 to about 50.
The invention further comprises a method of making an emulsion polymer comprising copolymerizing by emulsion polymerization a polymerizable surfactant, or a salt thereof, having the formula:
R1xe2x80x94C(O)xe2x80x94R2xe2x80x94X 
wherein:
R1 is an optionally substituted vinyl radical, preferably CH2xe2x95x90CHxe2x80x94, CH2xe2x95x90C(CH3)xe2x80x94, or cis-CH(COOH)xe2x95x90CHxe2x80x94,
R2 is a divalent polyoxyalkylene radical having at least two oxypropylene units, preferably about 2 to about 50 oxypropylene units, more typically about 2 to about 20 oxypropylene units, optional oxyethylene units in a block or random pattern, and a molar ratio oxypropylene units to oxyethylene units of at least about 2:1, preferably at least about 3:1, typically at least about 4:1 and more typically at least about 5:1, and
X is a phosphate xe2x80x94OPO3H2 group, wherein in the ester the mono-phosphate ester to di-phosphate ester weight ratio is greater than 80:20
with at least one other polymerizable monomer.
In one aspect, this invention relates to a method of making polymerizable phosphate ester compounds having the formula:
R1xe2x80x94C(O)xe2x80x94R2xe2x80x94OPO3H2 
wherein:
R1 is an optionally substituted vinyl radical, preferably CH2xe2x95x90CHxe2x80x94, CH2xe2x95x90C(CH3)xe2x80x94, or cis-CH(COOH)xe2x95x90CHxe2x80x94, and
R2 is a divalent polyoxyalkylene radical having at least two oxyalkylene units, preferably about 2 to about 50 oxyalkylene units, more typically about 2 to about 20 oxyalkylene units, e.g. (Oxe2x80x94CH2CH2)n or (Oxe2x80x94CH2CH(CH3))n wherein n is from about 2 to about 50, wherein in the ester the mono-phosphate ester to di-phosphate ester weight ratio is greater than 80:20.
The polyoxyalkylene unit can be derived from a variety of epoxyalkane compounds including ethylene oxide, propylene oxide, butylene oxide, styrene oxide, other alkyl, cycloalkyl or aryl substituted alkyl oxides or alkyl or aryl glycidyl ethers. It may additionally include hydrocarbon chain segments such as might be derived from ring opening of caprolactone by 2-hydroxyethyl methacrylate.
The method comprises the steps of:
a) preparing a slurry or paste reagent composition by intimately blending and exclusively reacting, at from about room temperature to about 80xc2x0 C. or the ultimate phosphation reaction temperature, an effective amount of phosphoric anhydride with from about 75 weight percent to about 117 weight percent phosphoric acid, said reagent composition having an effective equivalent polyphosphoric acid weight percent of from about 118 to about 125; and
b) reacting said reagent composition with at least one alcohol of the formula R1xe2x80x94C(O)xe2x80x94R2xe2x80x94Oxe2x80x94H, typically for a reaction time of from about 4 to about 12 hours;
wherein in the resulting ester compositions, the mono-ester to di-ester weight ratio is greater than 80:20 and the weight percent of the residual of said alcohol and phosphoric acid are individually each less than 6%.
In another aspect, this invention relates to a method of making polymerizable compounds having the formula:
R1xe2x80x94C(O)xe2x80x94R2xe2x80x94OPO3H2 
wherein:
R1 is an optionally substituted vinyl radical, preferably CH2xe2x95x90CHxe2x80x94, CH2xe2x95x90C(CH3)xe2x80x94, or cis-CH(COOH)xe2x95x90CHxe2x80x94, and
R2 is a divalent polyoxyalkylene radical having at least two oxyalkylene units, preferably about 2 to about 50 oxyalkylene units, more typically about 2 to about 20 oxyalkylene units, e.g. (Oxe2x80x94CH2CH2)n or (Oxe2x80x94CH2CH(CH3))n wherein n is from about 2 to about 50;
said method comprising the steps of:
A) preparing a phosphoric acid-alcohol reactant solution by
i) dissolving
a) from about 75 weight % to about 117 weight % phosphoric acid in
b) at least one alcohol medium of the formula R1xe2x80x94C(O)xe2x80x94R2xe2x80x94Oxe2x80x94H, wherein R1 and R2 are as defined above, under essentially non-reactive temperature conditions;
B) then
ii) intimately blending a stoichiometrically effective amount of phosphoric anhydride into said reactant solution and
iii) reacting exclusively the phosphoric acid in said reactant solution with the stoichiometrically effective amount of phosphoric anhydride to produce in-situ a phosphation reagent having an effective equivalent polyphosphoric acid weight percent of from about 118 to 125; and
C) reacting the phosphation reagent so produced with the alcohol medium, typically at from about 75xc2x0 C. to about 100xc2x0 C. for a reaction time of from about 4 to about 12 hours,
wherein in the resulting ester compositions, the mono-ester to di-ester weight ratio is greater than 80:20 and the weight percent of the residual of said alcohol and phosphoric acid are individually each less than 6%.
Latices, water based dispersions of polymers obtained by emulsion polymerization, are widely used in various applications such as paints, adhesives, paper coatings, and carpet backing. Although some applications do not require it, the major property of the latex is its ability to bind various substrates. Thus, adhesion is a key factor, and one of the most difficult aspects is the wet adhesion. The latter is strongly affected by the presence of surfactant needed during the polymerization and remains one of the big challenges for latices. Surfactants affect adhesion and wet adhesion in various ways.
One way is by migrating to the interfaces during the drying process. At the interface between the coating and the substrate, it will reduce adhesion by forming double layers that are less adhesive and more sensitive to external water. This effect can totally ruin the properties of the coating. At the interface of coating/air, it reduces the interfacial tension of the coating, allows water to spread easily on the surface, and increases the water diffusion through this interface.
Another way is by forming interconnected clusters in the coating. Surfactants are very often incompatible with the coating and the pigments and have a tendency to segregate during and after the drying process. One of the negative aspects is that due to differences in refractive index, it will create haze in the coating, which is very detrimental in the clear coat type (adhesives for coatings). The major problem is the tremendous ability of these clusters to carry water throughout the film and to the interface film/substrate which impairs the mechanical properties, particularly adhesion, of the coating.
Beside this, surfactants can increase foaming and require the addition of a defoamer that may have other inconveniences such as the dewetting of the coating (such as the formation of fish eyes in the paint film). Finally, there are very often cross interactions in the coatings that may induce migration of the latex surfactants to the pigments leading to a destabilization of the paint. This phenomenon is detrimental to paint quality as well as to water resistance. Unfortunately, even though some trials have been done at the lab scale to run emulsion polymerization without surfactant, no known industrial process is known for doing so. Surfactant remains a necessary evil. Some decades ago, functional monomers with stabilizing groups (carboxylic, sulfate, sulfonate and the like) appeared and helped to reduce the amount of surfactant significantly thus improving properties. However, they are not surface active materials and thus are not able to stabilize the pre-emulsions of monomers or to be used solely during the nucleation period.
The high mono/di-ester polymerizable phosphated monomers of this invention makes it possible to eliminate traditional emulsifiers employed in emulsion polymerization and eliminate or avoid the problem or drawbacks associated with their presence in the resulting latices to be used for paints or coatings.
In another aspect, this invention relates to a method of making an emulsion polymer comprising copolymerizing by emulsion polymerization a polymerizable surfactant, or a salt thereof, having the formula:
R1xe2x80x94C(O)xe2x80x94R2xe2x80x94X 
wherein:
R1 is an optionally substituted vinyl radical, preferably CH2xe2x95x90CHxe2x80x94, CH2xe2x95x90C(CH3)xe2x80x94, or cis-CH(COOH)xe2x95x90CHxe2x80x94,
R2 is a divalent polyoxyalkylene radical having at least two oxypropylene units, preferably about 2 to about 50 oxypropylene units, more typically about 2 to about 20 oxypropylene units, optional oxyethylene units in a block or random pattern, and a molar ratio oxypropylene units to oxyethylene units of at least about 2:1, preferably at least about 3:1, typically at least about 4:1 and more typically at least about 5:1, and
X is a phosphate xe2x80x94OPO3H2 group, wherein in the ester the mono-phosphate ester to di-phosphate ester weight ratio is greater than 80:20 with at least one other polymerizable monomer
The polymerizable surfactant can be made by different routes. For example, a preferred polymerizable surfactant wherein X is a phosphate xe2x80x94OPO3H2 group can be made by phosphation of the product of esterification of a polyalkylene glycol with a vinyl-functional carboxylic acid, or anhydride or acid halide thereof. The phosphation is preferably conducted as disclosed in U.S. Pat. Nos. 5,463,101, 5,550,274 and 5,554,781, as well as in EP Patent publication number EP 0 675,076 A2, especially as described in Example 18 of the EP publication. A polymerizable surfactant wherein X is a sulfate xe2x80x94OSO3H2 group or sulfonate xe2x80x94SO3H group can be made by sulfating one of the hydroxyl groups of a polyalkylene glycol, or replacing said hydroxyl group with a sulfonate group, and then esterifying the remaining hydroxyl group of said polyalkylene glycol with a vinyl-functional carboxylic acid, or anhydride or acid halide thereof.
The polymerizable surfactants are ethylenically unsaturated and, thus, are polymerizable through this unsaturation. The monomer may be useful in a variety of homopolymers and copolymers, e.g. those produced by solution, bulk or suspension polymerization, but should be most useful as a comonomer in the production of latices of low crosslinking density through emulsion polymerization. Emulsion polymerization is discussed in G. Pohlein, xe2x80x9cEmulsion Polymerizationxe2x80x9d, Encyclopedia of Polymer Science and Engineering, vol. 6, pp. 1-51 (John Wiley and Sons, Inc., N.Y., N.Y., 1986), the disclosure of which is incorporated herein by reference. Emulsion polymerization is a heterogeneous reaction process in which unsaturated monomers or monomer solutions are dispersed in a continuous phase with the aid of an emulsifier system and polymerized with free-radical or redox intiators. The product, a colloidal dispersion of the polymer or polymer solution, is called a latex.
The comonomers which are typically employed include such monomers as methyl acrylate, ethyl acrylate, methyl methacrylate, butyl acrylate, 2-ethyl hexyl acrylate, other acrylates, methacrylates and their blends, acrylic acid, methacrylic acid, styrene, vinyl toluene, vinyl acetate, vinyl esters of higher carboxylic acids than acetic acid, e.g. vinyl versatate, acrylonitrile, acrylamide, butadiene, ethylene, vinyl chloride and the like, and mixtures thereof.
In the above process, suitable initiators, reducing agents, catalysts and surfactants are well known in the art of emulsion polymerization. Typical initiators include ammonium persulfate (APS), hydrogen peroxide, sodium, potassium or ammonium peroxydisulfate, dibenzoyl peroxide, lauryl peroxide, ditertiary butyl peroxide, 2,2xe2x80x2-azobisisobutyronitrile, t-butyl hydroperoxide, benzoyl peroxide, and the like.
Suitable reducing agents are those which increase the rate of polymerization and include for example, sodium bisulfite, sodium hydrosulfite, sodium formaldehyde sulfoxylate, ascorbic acid, isoascorbic acid, and mixtures thereof.
Suitable catalysts are those compounds which increase the rate of polymerization and which, in combination with the above-described reducing agents, promote decomposition of the polymerization initiator under the reaction conditions. Suitable catalysts include transition metal compounds such as, for example, ferrous sulfate heptahydrate, ferrous chloride, cupric sulfate, cupric chloride, cobalt acetate, cobaltous sulfate, and mixtures thereof.
Suitable surfactants which may be used in conjunction with the polymerizable surfactant include ionic and nonionic surfactants such as alkyl polyglycol ethers such as ethoxylation products of lauryl, tridecyl, oleyl, and stearyl alcohols; alkyl phenol polyglycol ethers such as ethoxylation products of octyl- or nonylphenol, diisopropyl phenol, triisopropyl phenol; alkali metal or ammonium salts of alkyl, aryl or alkylaryl sulfonates, sulfates, phosphates, and the like, including sodium lauryl sulfate, sodium octylphenol glycolether sulfate, sodium dodecylbenzene sulfonate, sodium lauryldiglycol sulfate, and ammonium tritertiarybutyl phenol and penta- and octa-glycol sulfonates, sulfosuccinate salts such as disodium ethoxylated nonylphenol half ester of sulfosuccinic acid, disodium n-octyldecyl sulfosuccinate, sodium dioctyl sulfosuccinate, and the like.
A typical process of emulsion polymerization preferably involves charging water to a reactor and feeding as separate streams a pre-emulsion of the monomers and a solution of the initiator. A small amount of the pre-emulsion and a portion of the initiator may be charged initially at the reaction temperature to produce a xe2x80x9cseedxe2x80x9d latex. The xe2x80x9cseedxe2x80x9d latex procedure results in better particle-size reproducibility. Under xe2x80x9cnormalxe2x80x9d initiation conditions, that is initiation conditions under which the initiator is activated by heat, the polymerization is normally carried out at about 60-90xc2x0 C. A typical xe2x80x9cnormalxe2x80x9d initiated process, for example, could employ ammonium persulfate as initiator at a reaction temperature of 80xc2x12xc2x0 C. Under xe2x80x9credoxxe2x80x9d initiation conditions, that is initiation conditions under which the initiator is activated by a reducing agent, the polymerization is normally carried out at 60-70xc2x0 C. Normally, the reducing agent is added as a separate solution. A typical xe2x80x9credoxxe2x80x9d initiated process, for example, could employ potassium persulfate as the initiator and sodium metabisulfite as the reducing agent at a reaction temperature of 65xc2x12xc2x0 C.
In the above emulsions, the polymer preferably exists as a generally spherical particle, dispersed in water, with a diameter of about 50 nanometers to about 500 nanometers. Gel content can be determined using the method taught in U.S. Pat. No. 5,371,148, incorporated herein by reference. Glass transition temperature (Tg) is a calculated number based on the proportion of each monomer utilized and the corresponding Tg for a homopolymer of such a monomer. In addition to making emulsion polymers, it is contemplated that the polymerizable surfactants of the present invention can be used to form solution copolymers.
In particular, the polymerizable surfactants of this invention may be incorporated in effective amounts in aqueous polymer systems to enhance the stability of emulsions of the polymers. The commonly used monomers in making acrylic paints are butyl acrylate, methyl methacrylate, ethyl acrylate and the like. In acrylic paint compositions the polymer is comprised of one or more esters of acrylic or methacrylic acid, typically a mixture, e.g. about 50/50 by weight, of a high Tg monomer (e.g. methyl methacrylate) and a low Tg monomer (e.g. butyl acrylate), with small proportions, e.g. about 0.5% to about 2% by weight, of acrylic or methacrylic acid. The vinyl-acrylic paints usually include vinyl acetate and butyl acrylate and/or 2-ethyl hexyl acrylate and/or vinyl versatate. In vinyl-acrylic paint compositions, at least 50% of the polymer formed is comprised of vinyl acetate, with the remainder being selected from the esters of acrylic or methacrylic acid. The styrene/acrylic polymers are typically similar to the acrylic polymers, with styrene substituted for all or a portion of the methacrylate monomer thereof.